Laxatives

Question 1

What are the different types of laxatives?

Answer 1

1. Bulk-forming
2. Faecal softener
3. Osmotic
4. Stimulants

Question 2

Describe the action of bulk forming laxatives and name one drug that falls under this cateogory

Answer 2

Increase the bulk or weight of the faeces, which in turn stimulates the colon

e.g. Fybogel (ispaghula husk), methylcellulose, sterculia

Question 3

Describe the action of poo softening laxatives and name one drug that falls under this cateogory

Answer 3

Decreases surface tension by allowing increased penetration of intestinal fluids into the faeces (i.e. allow water to enter the faeces to soften it)

e.g. docusate sodium, glycerol suppositories, arachis oil (e.g. groundnut oil, peanut oil), liquid parrafin (as a lubricant. Should be used with caution due to its adverse effects e.g. anal seepage and risk of granulomatous disease)

Question 4

Describe the action of osmotic laxatives and name one drug that falls under this cateogory

Answer 4

Increases water in colon either by drawing water into it from the body or retaining the fluid they were administered with

e.g. Lactulose, inert polyethylene glycol (e.g. macrogols like macrogol 3350 with potassium chloride, sodium bicarbonate and sodium chloride)

Question 5

Describe the action of stimulant laxatives and name one drug that falls under this cateogory

Answer 5

Increase gut motility and often cause abdominal cramps

e.g. bisacodyl (a.k.a Duclolax), senna (a.k.a Senokot), sodium picosulfate, co-danthramer and co-danthrusate (which are limited to use to terminally ill patients due to potential carcinogenecity and genotoxicity)